Add cuco::detail::stream_sync(cuda::stream_ref) to centralize CCCL version-specific API naming

[sleeepyjack]

Fourth verbatim copy of this CCCL-version sync switch (three in static_multimap.inl); a cuco::detail::stream_sync(cuda::stream_ref) helper would centralize it.

Originally posted by @PointKernel in #839 (comment)